[SI-LIST] : Obtaining estimated parasitics for capacitors (formerly High Speed AC Coupling)

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From: Zabinski, Patrick J. (zabinski.patrick@mayo.edu)
Date: Wed Nov 01 2000 - 04:56:22 PST


Alex,

Here are three capacitor vendor sites offering tools to help obtain
estimated parasitics (ESR, ESL, etc.) and performance (impedance magnitude)
for their caps.

http://www.avxcorp.com/SpiApps/default.asp

http://www.kemet.com/kemet/web/homepage/kechome.nsf/vabypagename/spicesoft

http://www.atceramics.com/designsupport/index.html

I've used all three, and it appears AVX SpiCap assumes a single, common ESL
for
a given package style (e.g., 0805 = 1.0 nH) regardless of capacitance.
However,
to obtain different capacitance values, the physical structure must change
(thinner
dielectrics, additional layers, etc.), so the inductance much change
accordingly.

Kemet's ESL values do change with different capacitance values (which leads
me to believe they've done a bit more work on their part), but as they
clearly state (Kemet: thanks for being clear on this) that their inductance
is obtained slightly different than others; thus their published values will
be slightly higher than those from other companies (by about 600 pH). If
I am reading between the lines of their explanation correctly, the ~600 pH
they add is related to return-path inductance.

I haven't tried the ATC software in quite some time, but if I recall
correctly,
it did not have useful information on multilayer chip caps (e.g., 0805).
They
might have updated their tools/database since I last use it.

Anyone know of other/additional tools? Does anyone have a different
opinion of
or experience with these three tools? Are there similar tools for resistors
and inductors?

Pat

P.S. I have access to these, I simply did not at the time I was
responding to you last night, so don't worry about sending me a copy.

>
>Hi Patrick,
>Thanks for getting back to me. Could you elaborate on the access to one of
the shareware routines
>on cap parasitics. Is this a software program? If you point me in the
right direction, I will
>get it and be glad to share it with you since you don't have access.>
>Thanks,
>Alex
>

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